Windows Communication Foundation, or just WCF, is a programming framework used to build applications that inter-communicate. WCF is the part of the .NET Framework dedicated to communications.



Originally tagged with the code name "Indigo", WCF is one of the four new application programming interfaces introduced with .NET Framework 3.0, which was released in December 2006.

In programming code, a WCF Service is implemented as a class. The class typically implements a Service Contract - a specially annotated interface whose methods stipulate the operations that the service performs. Learn more of this with the .

Typically, the methods on the interface accept inputs and output messages, which conform to Data Contracts, described with specially annotated classes. Think of these as Data Transfer Objects.

The Data and Service Contracts are defined using annotations in programming code, known formally in .NET as Attributes. Any class that is to be exposed as a WCF service must be either marked with the ServiceContract attribute, or implement an interface marked with it.

All methods in the class or interface that a client can invoke using SOAP messages must be marked with OperationContract attribute. All classes or structures that define the data to be passed into or out of the operations are marked with the DataContract attribute.

The attributes support the automatic generation of WSDL descriptions for the exposed methods, which can then be accessed by clients, or advertised to them. Visit the for more information about this.

A service can expose multiple Service Contracts. This can be done by defining multiple .NET interfaces, each marked as a Service Contract. The service class can then implement all the interfaces.

All Service Contracts have an associated implicit or explicit Data Contract which defines the data that the service works on. If the parameters accepted and returned by the service methods consist of primitive types, then the Data Contract is defined implicitly by WCF.

If, on the other hand, the data is of a complex type like an object or a struct, then it must be defined explicitly by the programmer via attributes. Data contracts specify how the data is serialized and de-serialized, allowing for custom representation of objects passing in and out.

A Data contract is defined by using a DataContract attribute on a class or structure. Members of the data structure which will be used by the service need to be marked with the DataMember attribute. For more detailed information about the Windows Communication Foundation and about .NET Framework, then visit the .